The Dami cell possesses the platelet collagen receptor VLA-2, but does not mobilize calcium

Flow cytometric and Western blot analysis showed that Dami cells possess the major platelet collagen adhesion receptor, the integrin VLA-2, and that VLA-2 was expressed in higher levels in a time-dependent manner in DMSO-induced Dami cells. Both control and DMSO-induced Dami cells were able to adhere to collagen as measured in a microtiter-based adhesion assay. It appeared that collagen adhesion was solely mediated by VLA-2, since inclusion of a monoclonal antibody directed against the alpha-2 subunit of VLA-2 in the adhesion assay was able to totally inhibit adhesion. Although Dami cells possess a variety of platelet markers, and are able to mobilize intracellular calcium in response to ADP, U-46619, and thrombin, they were unable to respond to collagen challenge. We concluded that Dami cells may lack some key transducing element present in platelets that prevents them from being activated by collagen.